The invention relates to a backrest structure for a seat, in particular to a backrest structure for a motor vehicle seat, and to a backrest module for a backrest frame of a backrest structure.
A backrest structure of this kind comprises a backrest frame which has a support structure and a front side facing the back of a seat user. Along the front side of the backrest frame the spinal column of the seat user extends in a longitudinal direction of the seat back when the seat is in use. The backrest structure furthermore comprises a backrest cushion at the backrest frame, a lumbar support mounted on the front side of the backrest frame for supporting the back of a seat user and an adjusting device for adjusting the position of the lumbar support perpendicular to the extension plane of the backrest frame.
In order to adjust the curvature of the backrest cushion, which is mounted in front of the backrest frame, more comfortably for a seat user such a backrest structure additionally comprises a curving element e.g., in the form of a flexible or elastic mat. This curving element is arranged between the lumbar support and the backrest cushion and is secured to the support structure of the backrest frame. The adjusting device acts on the curving element in order to adjust a curvature of the curving element and thus a curvature of the backrest cushion. In this way, a curving element serves for a distribution of the pressure applied by the adjusting device.
The curving element in such a backrest structure is usually just clipped or plugged to the support structure of the backrest frame which furthermore is preferably designed in the form of a wire frame. The curving element may hence be easily mounted to the support structure of the backrest frame. Such is in particular advantageous since the adjusting device has normally to be assembled and fixed to the support structure prior to the mounting of the curving element so that the curving element—seen from the front side of a backrest facing a seat user—at least partially covers the assembled adjusting device.
Due to the simple connection of the curving element to a support structure of the backrest frame it is, however, often mandatory to provide a backrest structure with additional sound dampeners, e.g. felt pads, tape or wire flock, to avoid rattling noises when the seat backrest is in an unloaded state and not occupied by a seat user. The connection between the support structure and the curving element allows for a marginal relative movement of the curving element with respect to the support structure so that the curving element is not in contact with support structure and thus could audibly abut against or hit the support structure when the unloaded seat backrest is moved, for example during a ride in the case of a backrest of a motor vehicle seat.
One solution to this problem could be to increase the pre-load applied on the curving element via a backrest cushion. Such an approach is, however, not very effective and cannot reliably ensure that the curving element is maintained in a constant position at the support structure since the backrest cushion (or a foam inside the backrest cushion) may disadvantageously be deformed or compressed over the time of use.
It is thus an object of the present invention to improve a backrest structure of the type mentioned with regard to the minimization of rattling noises caused by a curving element of the backrest structure which is secured to a support structure of a backrest frame.